Trends and Racial/Ethnic, Socioeconomic, and Geographic Disparities in Maternal Mortality from Indirect Obstetric Causes in the United States, 1999-2017

BACKGROUND: This study examines trends and inequalities in US maternal mortality from indirect obstetric causes (ICD-10 codes: O98-O99) and specific chronic conditions by maternal race/ethnicity, socioeconomic status, nativity/immigrant status, marital status, place and region of residence, and cause of death. METHODS: National vital statistics data from 1999 to 2017 were used to compute maternal mortality rates by sociodemographic factors. Rate ratios and log-linear regression were used to model mortality trends and differentials. RESULTS: During 1999-2017, maternal mortality from indirect causes showed an upward trend; the annual rates increased by 11.2% for the overall population, 12.9% for non-Hispanic Whites, and 9.4% for non-Hispanic Blacks. The proportion of all maternal deaths due to indirect causes increased from 12.0% in 1999 to 26.9% in 2017. Maternal mortality from CVD increased sharply over time, from 0.40/100,000 live births in 1999 to 1.82 in 2017. During 2013-2017, compared to non-Hispanic Whites, non-Hispanic Blacks had 83% higher, Hispanics 51% lower, and Asian/Pacific Islanders 55% lower mortality from indirect causes. Non-Hispanic White women with <12 years of education had 4.4 times higher mortality than those with a college degree. Unmarried, US-born, and women living in rural areas and deprived areas had 90%, 80%, 60%, and 97% higher maternal mortality risks than married, immigrant, and women in urban areas and affluent areas, respectively. Maternal mortality from infectious diseases, including HIV, was 4.1 times greater and from respiratory diseases 2.9 greater among non-Hispanic Black women compared to non-Hispanic White women. CONCLUSIONS AND GLOBAL HEALTH IMPLICATIONS: While maternal mortality from direct obstetric causes has declined during the past two decades, maternal deaths due to indirect causes, particularly from pre-existing medical conditions, including CVD and metabolic disorders, have increased. Understanding complex interactions among social determinants, indirect causes, and proximate/direct causes is important to reducing maternal mortality and improving maternal health.